What is USSD in telecom?

Most of the people don’t know about USSD. In Telecom, USSD is nothing but a protocol used in GSM mobile phones for communicating with service provider’s PC. USSD stands for Unstructured Supplementary Service Data which can be used in WAP browsing, independent callback services, balance checking, local menu-based content services etc. It is a message which is similar to short message service (SMS) consists of 182 alphanumeric characters in length. But USSD is more responsive than the services that used in SMS. USSD Message is a flash message which don’t store in phone and expires after 20 sec. So reply will accept before the expiry time of message. You can also access real-time updates from social networking sites like face book, twitter and LinkedIn. These USSD messages can be pushed through USSD Gateway.
USSD Gateway:
USSD Gateway is known as electrical switch which controls several different protocols or communications signals and routed based upon several different parameters. It routes USSD messages from the signaling network to service applications and vice versa. For using this gateway we have know what session is going on. It also locates where the mobile station is currently. The functionality of USSD is well available on roaming networks and the messages will be routed back to home HLR. It works in two modes i.e., pull and push modes.